Great-tailed Grackles are flexible foragers that can eat many different types of food. They can eat bugs, small land animals, and eggs. They can remove parasites from large animals. They can eat fruit and seeds. They can hunt small birds in flight. They can wade in shallow water to catch fish. They can even hunt for fish by flying close to water!

During breeding season, dominant males will defend a territory. Several females can build nests inside that territory and raise their own chicks.

For nesting, females make a cup nest out of plant materials, situated high in a tree.  Females lay 4 to 7 blue-grey speckled eggs. Incubation lasts 13 to 14 days, and the chicks are able to leave the nest within 12 to 17 days. The chicks are fed by their parents for several more weeks after leaving the nest.

Traditionally this species lived in Central America, but they are able to live in a diverse range of tropical habitats. They are adaptable to human disturbance. Their habitat flexibility has led to their range increasing dramatically into North America as humans create more farms and cities. This species is considered Least Concern on the IUCN Red List due to its extremely large and expanding range.